#include "vpg.h"
...
cv::VideoCapture capture;

if(capture.open(0)) { // open default video capture device	
	vpg::FaceProcessor faceproc(CASCADE_FILENAME); // CASCADE_FILENAME is a path to haarcascade or lbpcascade for the face detection
	double framePeriod = faceproc.measureFramePeriod(&capture); // measure discretization period of the video in milliseconds
	vpg::PulseProcessor pulseproc(framePeriod); // object that performs harmonic analysis of vpg-signal
	cv::Mat frame;
	unsigned int k = 0; // it is counter of enrolled frames
	double s = 0.0, t = 0.0; // this is variables for temporal results storing ('s' for vpg-signal count, 't' for actual frame time)
	while(true) {
		if(capture.read(frame)) {
			faceproc.enrollImage(frame, s, t); // perform face detection, then skin detection, then average skin pixels
			pulseproc.update(s,t); // update vpg-signal
			cv::rectangle(frame,faceproc.getFaceRect(),cv::Scalar(255,255,255)); // draw target rect
			cv::imshow("Video probe", frame);
	        }
	        if(k % 64 == 0) {
		        std::printf("\nHR measurement: %d bpm\n\n", pulseproc.computeFrequency()); // compute and print heart rate estimation
		}
	        k++;
		int c = cv::waitKey(1.0); // enroll user input
		if( (char)c == '27' )  {// use need to press escape for the exit 
			break;
		}
	}
}
...